Update README.md

Asjad-J · web-flow · commit 21b2f0127aa7 · 2022-01-23T10:08:00.000+05:00
add link back to article: Hidden Classes in Java 15
diff --git a/core-java-modules/core-java-15/README.md b/core-java-modules/core-java-15/README.md
@@ -4,4 +4,5 @@ This module contains articles about Java 15.
 
 ### Relevant articles
 
+- [Hidden Classes in Java 15](https://www.baeldung.com/java-hidden-classes)
 - [Sealed Classes and Interfaces in Java 15](https://www.baeldung.com/java-sealed-classes-interfaces)

Original file line number	Diff line number	Diff line change
`@@ -4,4 +4,5 @@ This module contains articles about Java 15.`
`4`	`4`
`5`	`5`	`### Relevant articles`
`6`	`6`
	`7`	`+- [Hidden Classes in Java 15](https://www.baeldung.com/java-hidden-classes)`
`7`	`8`	`- [Sealed Classes and Interfaces in Java 15](https://www.baeldung.com/java-sealed-classes-interfaces)`